A 3D coupled thermo-mechanical and neutron diffusion numerical model for irradiated concrete

This paper presents a Finite Element-based formulation for assessing the behavior of irradiated cementitious materials under operational conditions, including both thermo-mechanical and neutron diffusion processes. Specifically, the mathematical model employs a two-group neutron diffusion theory in conjunction with heat conduction theory. This methodology accounts for the transition of fast neutrons to thermal neutrons and the associated heat generation resulting from the absorption of thermal neutrons during radiation exposure. The 3D coupled model is solved monolithically, as a single, integrated system. This proposed formulation addresses a significant gap in commercial software by enabling the analysis of multiphysics scenarios using a single tool. Additionally, it currently represents a unique fully coupled 3D model based on the Finite Element Method for tackling this specific multiphysics problem. Through validation against existing literature results, this approach demonstrates accurate evaluation of the radiation field, temperature variations, and stress/strain states in irradiated concrete operating under service conditions. Furthermore, to investigate the material's durability, the proposed numerical formulation is extended to include mesomechanical studies.